Electronic camera

ABSTRACT

An imaging element which continuously outputs image data obtained by photoelectrically converting object light, a buffer memory which temporarily stores image data being output from the imaging element, a plurality of image processing units which are capable of performing image processing on image data output from the imaging element, and a control unit which causes an image processing unit of the plurality of image processing units to operate based on a number of pieces of the image data stored in the buffer memory when the image data is output continuously from the imaging element, in which the image processing unit performs image processing on each piece of image data output continuously.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2010-094317, filed on Apr. 15, 2010, theentire contents of which are incorporated herein by reference.

BACKGROUND

1. Field

The present application relates to an electronic camera that performsimage processing on image data obtained by shooting.

2. Description of the Related Art

Conventionally, in an electronic camera such as a digital camera, thereare provided a continuous shooting mode in which a plurality of stillimages is obtained continuously based on a frame rate set in advance, amoving image mode in which a moving image is obtained, etc., in additionto a shooting mode in which one still image is obtained. In a digitalcamera comprising such a continuous shooting mode and a moving imagemode, image data is output at regular intervals from an imaging element,and thus, if processing capacity relating to image processing or codingprocessing for output image data is low, processing time required forthe processing increases and as a result, processing on image data notsubjected to processing yet is performed even after shooting has beencompleted. Because of this, it is devised that two image processingunits that perform image processing are arranged in parallel and imageprocessing on image data is performed while distributing image dataoutput from the imaging element to the image processing units,respectively (see Japanese Unexamined Patent Application Publication No.H5-227519). Because of this, the image processing capacity is improvedand the processing time required for image processing is reduced.

In contrast, a large amount of electric power is consumed in the imageprocessing for obtained image data, and thus, if image processing isperformed by using the above-described two image processing units, moreelectric power is consumed. Furthermore, the provision of two imageprocessing units is effective for image processing at the time ofcontinuous shooting and movie shooting, but at the time of shooting of astill image, image processing can be performed by one of the imageprocessing units and the other image processing unit does not performany image processing, and thus, electric power is wasted.

SUMMARY

A proposition of the present embodiment is to provide an electroniccamera capable of preventing electric power from being wasted when aplurality of image processing units is used.

In order to solve the above-described problems, an electronic camera ofthe present embodiment is characterized by including an imaging elementwhich continuously outputs image data obtained by photoelectricallyconverting object light, a buffer memory which temporarily stores imagedata being output from the imaging element, a plurality of imageprocessing units which are capable of performing image processing onimage data output from the imaging element, and a control unit whichcauses an image processing unit of the plurality of image processingunits to operate based on a number of the pieces of the image datastored in the buffer memory when image data is output continuously fromthe imaging element, in which the image processing unit performs imageprocessing on each piece of image data output continuously.

In addition, it is preferable that the plurality of the image processingunits include a first image processing unit which operates regardless ofan output state of the image data output from the imaging element and asecond image processing unit operated by the control unit, and thecontrol unit causes the second image processing unit to operate based onthe number of pieces of the image data stored in the buffer memory.

Furthermore, it is preferable that the control unit causes the imageprocessing unit that performs image processing on each piece of theimage data output continuously to operate based on a result of acomparison between the number of pieces of the image data stored in thebuffer memory and a threshold value set in advance.

Moreover, it is preferable that the control unit causes the imageprocessing unit that performs image processing on each piece of theimage data output continuously to operate when the number of pieces ofthe image data stored in the buffer memory exceeds the threshold value.

Furthermore, an electronic camera of the present embodiment ischaracterized by including an imaging element which continuously outputsimage data obtained by photoelectrically converting object light, aplurality of image processing units which are capable of performingimage processing on image data output from the imaging element, and acontrol unit which causes an image processing unit of the plurality ofthe image processing units to operate based on an output interval of theimage data when the image data is output continuously from the imagingelement, in which the image processing unit performs image processing oneach piece of image data output continuously.

Moreover, it is preferable that the plurality of the image processingunits include a first image processing unit which operates regardless ofan output state of the image data output from the imaging element and asecond image processing unit operated by the control unit, and thecontrol unit causes the second image processing unit to operate based onthe output interval of the image data.

In addition, it is preferable that the control unit causes the imageprocessing unit that performs image processing on each piece of theimage data output continuously to operate based on a result of acomparison between the output interval of the image data and a thresholdvalue set in advance.

Furthermore, it is preferable that the control unit causes the imageprocessing unit that performs image processing on each piece of theimage data output continuously to operate when the output interval ofthe image data is less than or equal to the threshold value.

Moreover, it is preferable that the output interval of the image data isobtained by measuring a time from a vertical synchronizing signal outputat the time of start of imaging to a vertical synchronizing signal to beoutput next.

In addition, it is preferable to include a setting operation unit to beoperated when setting the output interval of the image data.

Furthermore, an electronic camera of the present embodiment ischaracterized by including an imaging element which continuously outputsimage data obtained by photoelectrically converting object light, aplurality of image processing units which are capable of performingimage processing on image data output from the imaging element, and acontrol unit which causes an image processing unit of the plurality ofimage processing units to operate based on an output resolution of theimage data output from the imaging element when the image data is outputcontinuously from the imaging element, in which the image processingunit performs image processing on each piece of image data outputcontinuously.

Moreover, it is preferable that the plurality of image processing unitsinclude a first image processing unit which operates regardless of anoutput state of image data output from the imaging element and a secondimage processing unit operated by the control unit, and the control unitcauses the second image processing unit to operate based on the outputresolution of the image data.

Furthermore, it is preferable that the control unit causes the imageprocessing unit that performs image processing on each piece of theimage data output continuously to operate based on a result of acomparison between the output resolution of the image data and athreshold value set in advance.

In addition, it is preferable that the control unit causes the imageprocessing unit that performs image processing on each piece of theimage data output continuously to operate when the output resolution ofthe image data exceeds the threshold value.

Furthermore, it is preferable that the control unit stops the imageprocessing unit operated by the control unit when image processing iscompleted in at least each of the image processing units operated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an outline of a configuration of a digitalcamera using the present embodiment.

FIG. 2 is a timing chart at the time of shooting in a continuousshooting mode in a first embodiment.

FIG. 3 is a timing chart at the time of shooting in a continuousshooting mode in a second embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS First Embodiment

FIG. 1 shows an example of a digital camera using the present invention.It is made possible for a digital camera 10 of the present invention toperform movie shooting to obtain a moving image in addition to stillimage shooting to obtain one still image at the time of operation of arelease button 55, to be described later, continuous shooting tocontinuously obtain a predetermined number of still images at regularintervals at the time of full-press operation of the release button 55,to be described later. Explanation will be given below on the assumptionthat a mode to perform still image shooting is referred to as a stillimage mode, a mode to perform continuous shooting as a continuousshooting mode, and a mode to perform movie shooting as a moving imagemode. Furthermore, explanation is given on the assumption that an actionto obtain an image by the digital camera 10 is referred to as shootingand the internal processing of the digital camera 10 performed at thetime of shooting as imaging.

As already known, the digital camera 10 photoelectrically convertsobject light taken in by an imaging optical system 15 through the use ofan imaging element 16 and obtains image data from an electric signalafter the photoelectric conversion. The imaging optical system 15includes a lens group including a zoom lens, a focus lens, etc., notshown schematically. The zoom lens and focus lens are moved in thedirection of an optical axis L by a lens drive mechanism, not shownschematically.

The imaging element 16 includes, for example, a CCD (Charge CoupledDevice), CMOS (Complementary Metal-Oxide Semiconductor), etc. The driveof the imaging element 16 is controlled by a driver 21. The control ofthe drive of the imaging element 16 includes the control of accumulationof signal charges and output of accumulated signal charges, in eachpixel of the imaging element 16. Explanation will be given below on theassumption that a signal charge output from the imaging element 16 isreferred to as an image signal. Furthermore addition to the above, thedriver 21 controls whether to drive all the pixels or part of the pixelsof the imaging element 16. That is, at the time of shooting, an imagesignal is obtained by driving all the pixels of the imaging element 16and at the time of non-shooting, an image signal is obtained byselectively using part of the pixels of the imaging element 16, that is,by so-called thinning control.

An AFE (Analog Front End) circuit 22 is configured to include an AGCcircuit and a CDS circuit, not shown schematically. The AFE circuit 22converts an analog signal into a digital signal by an A/D conversioncircuit, not shown schematically, after performing analog processing,such as gain control and noise removal, on an input image signal. Thedigital image signal is output to a DFE circuit 23.

The DFE (Digital Front End) circuit 23 performs noise correctionprocessing and defect correction processing on an input image signal.The image signal having been subjected to the processing is output to afirst image processing circuit 31 and a second image processing circuit36, respectively. Explanation is given below on the assumption that animage signal to be input to the first image processing circuit 31 andthe second image processing circuit 36, respectively, is referred to asimage data. Reference numeral 24 represents a timing generator (TG) andupon receipt of an output of a timing pulse of the TG 24, the operationsof the driver 21, the AFE circuit 22, and the DFE circuit 23 aresynchronized.

The first image processing circuit 31 starts to operate when the mainpower source of the digital camera 10 is turned on and stops itsoperation when the main power source of the digital camera 10 is turnedoff. The first image processing circuit 31 performs image processing andcoding processing on image data stored in a first buffer memory 41 andat the same time, performs decoding processing on decoded data in animage file stored in a storage medium 51 and image processing for imagedata having been subjected to decoding processing. The first imageprocessing circuit 31 has functions of a control unit 32, an imageprocessing unit 33, and a coding/decoding unit 34.

The control unit 32 supplies electric power from a power source device57 to the first buffer memory 41 as well as to the image processing unit33, the coding/decoding unit 34. Furthermore, the control unit 32outputs a clock pulse to the first buffer memory 41 as well as to theimage processing unit 33 and the coding/decoding unit 34. Because ofthis, the operation of each part of the first image processing circuit31 and the first buffer memory 41 is controlled by the control unit 32.Moreover, the control unit 32 outputs an operation signal or anoperation stop signal to the second image processing circuit 36. Becauseof this, the second image processing circuit 36 is switched between astate where it operates (hereinafter, referred to as an operation state)and a state where its operation is stopped (hereinafter, referred to asa standby state).

The image processing unit 33 performs image processing, such as whitebalance processing, color interpolation processing, gamma processing,and contour enhancement processing, on image data stored in a firststorage region 42. This processing is already known, and thus, itsdetails are omitted here.

The coding/decoding unit 34 compresses and codes image data having beensubjected image processing by the image processing unit 33. Thecompressed and coded image data is referred to as coded datahereinafter. The decoded data is written to a second storage region 43of the first buffer memory 41. When image data obtained in thecontinuous shooting mode and the moving image mode is input, a pluralityof pieces of image data is input, and thus, in these modes, image dataand coded data are managed by an output number etc. The coding/decodingunit 34 generates image data by decoding coded data read from thestorage medium 51.

The second image processing circuit 36 switches between the standbystate and the operation state upon receipt of the operation signal orthe operation stop signal from the first image processing circuit 31.For example, in the standby state, electric power is supplied only to acontrol unit 37, to be described later, and no electric power issupplied to an image processing unit 38 or coding/decoding unit 39.Because of this, even if image data from the DFE circuit 23 is input,this image data is invalid data that is not written to a second buffermemory 45. In contrast, in the operation state, electric power issupplied to the image processing unit 38 and the coding/decoding unit 39in addition to the control unit 37. In this case, for example, every twopieces of image data to be input is handled as valid image data andwritten to the second buffer memory 45. Image data not to be written tothe second buffer memory 45 is invalid image data.

Like the first image processing circuit 31, the second image processingcircuit 36 includes the control unit 37, the image processing unit 38,and the coding/decoding unit 39. The functions of the image processingunit 38 and the coding/decoding unit 39 in the second image processingcircuit 36 are the same as the functions of the image processing unit 33and the coding/decoding unit 34 in the first image processing circuit31, respectively, and thus, their details are omitted here. Theprocessing capacity of the image processing according to the imageprocessing unit 38 is the same as the processing capacity of the imageprocessing according to the first image processing circuit 31.

The control unit 37 controls each part of the second image processingcircuit 36 by outputting a clock pulse as well as supplying electricpower from the power source device 57 to the image processing unit 38and the coding/decoding unit 39. It should be noted that to the controlunit 37, electric power is supplied from the power source device 57 evenin the standby state. Because of this, it is made possible to identifyan operation signal input from the first image processing circuit 31even if the second image processing circuit 36 is in the standby state.It should be noted that when the second image processing unit 36 is inthe standby state, no electric power is supplied to the image processingunit 38 or the coding/decoding unit 39, and thus, processing is notperformed on each of these parts. Furthermore, even if the second imageprocessing unit 36 is in the standby state, image data from the DFEcircuit 23 is input, but the control unit 37 processes input image dataas invalid data. Moreover, upon receipt of the operation signal from thefirst image processing circuit 31, the control unit 37 starts to supplyelectric power to each part of the second image processing circuit 36and the second buffer memory 45 and at the same time, outputs a clockpulse to the image processing unit 38, the coding/decoding unit 39, andthe second buffer memory 45. Because of this, the operation of each partof the first image processing circuit 31 and the operation of the firstbuffer memory 41 are controlled by the control unit 32.

Furthermore, the control unit 37 reads coded data stored in a secondstorage region 47 of the second buffer memory 45 and outputs it to thefirst image processing circuit 31 when image processing and codingprocessing are performed on all the image data stored in the firststorage region 46 of the second buffer memory 45. This coded data isstored in the second storage region 43 of the first buffer memory 41 viathe first image processing circuit 31. When all the coded data stored inthe second buffer memory 45 is output to the first image processingcircuit 31, an operation stop signal is input from the first imageprocessing circuit 31. Upon receipt of the operation stop signal, thecontrol unit 37 stops outputting of a clock pulse to the imageprocessing unit 38, the coding/decoding unit 39, and the second buffermemory 45 and stops the supply of electric power thereto. Because ofthis, the operations of the image processing unit 38, thecoding/decoding unit 39, and the second buffer memory 45 are stopped.That is, the second image processing circuit 36 switches from theoperation state to the standby state.

The first buffer memory 41 includes the first storage region 42 and thesecond storage region 43. In the first storage region 42, image dataoutput from the DFE circuit 23 is stored. In contrast, in the secondstorage region 43, coded data generated by the first image processingcircuit 31 is stored. Furthermore, in the second storage region 43,coded data input to the first image processing circuit 31 via the secondimage processing circuit 36 is also stored. It should be noted thatsimilarly, the second buffer memory 45 also includes the first storageregion 46 and the second storage region 47. Data stored in these storageregions is the same as that in the first buffer memory 41.

In the storage medium 51, a still image file and a moving image file arestored. These image files include image files in which coded data storedin the first buffer memory 41 described above and additionalinformation, such as information about shooting conditions, shootingdate, and the type of the digital camera 10, etc., are combined.

An LCD 52 is one form of a display device and displays a through imageor an image obtained at the time of shooting. It should be noted that animage obtained at the time of shooting includes, for example, athumbnail image. The thumbnail image is an image generated by performingreduction processing on image data obtained by shooting. Furthermore, inaddition to the above, the LCD 52 displays an image for setting used tomake settings of the digital camera 10.

A CPU 54 totally controls each part of the digital camera 10 byexecuting a control program, not shown schematically. To the CPU 54, therelease button 55, a setting operation unit 56, etc., are connected andthe CPU 54 controls each part of the digital camera 10 based on theoperation request by these operation members and the control program.For example, when the release button 55 is operated, after AE processingand AF processing are performed, imaging processing is performed underthe exposure condition determined by the AE processing. Furthermore,when the setting operation unit 56 is operated, it is possible to changevarious settings in the digital camera 10. At the time of the setting,any of the shooting modes is selected or the reproduction mode isselected, and a frame rate value in the continuous shooting mode ormoving image mode is set.

When the main power source of the digital camera 10 is turned on, thepower source device 57 supplies electric power to each part of thedigital camera 10. Moreover, when the main power source of the digitalcamera 10 is turned off, the power source device 57 stops the supply ofelectric power to each part of the digital camera 10.

Next, the flow of processing in the first image processing circuit 31and the second image processing circuit 36 when shooting is performed inthe continuous shooting mode in the first embodiment is explained usingthe timing chart in FIG. 2. It should be noted that in the timing chartin FIG. 2, a case is explained, where 10 images are shot continuously inthe continuous shooting mode at a frame rate value of 8 fps. Meanwhile,a frame image in FIG. 2 corresponds to image data shown in FIG. 1. Thatis, a frame image 1 corresponds to first image data shown in FIG. 1 anda frame image 2 corresponds to second image data shown in FIG. 1,respectively. Immediately before the timing chart in FIG. 2 isperformed, the second image processing circuit 36 is in the standbystate.

When the release button 55 is operated, a release switch (SW) is turnedON and after AE processing and AF processing are performed, shooting isperformed under the shooting conditions set by the AE processing. Itshould be noted that because of the shooting in the continuous shootingmode, the above-described imaging is performed continuously a pluralityof times based on the frame rate value set in advance. At each time ofthe imaging performed a plurality of times, the signal chargephotoelectrically converted in the imaging element 16 is output from theimaging element 16 to the AFE circuit 22 as an image signal. The imagesignal input to the AFE circuit 22 is subjected to analog processing,such as gain control and noise removal, and converted into a digitalsignal. After that, the image signal converted into the digital signalis output to the DFE circuit 23 from the AFE circuit 22. The imagesignal converted into the digital signal is output to the first imageprocessing circuit 31 and the second image processing circuit 36,respectively, after having been subjected to noise correction processingand defect correction processing in the DFE circuit 23. It should benoted that because the second image processing circuit 36 is in thestandby state, the image signal input from the DFE circuit 23 to thesecond image processing circuit 36 is an invalid signal (data).

In contrast, the image data input to the first image processing circuit31 is written to the first storage region 42 of the first buffer memory41. For example, when the image signal is one obtained by the firstimaging, the number of pieces of image data stored in the first storageregion 42 of the first buffer memory 41 is 1.

Then, when 0.125 seconds elapse after the first imaging, the secondimaging is performed. Image data based on the second imaging is writtento the first storage region 42 of the first buffer memory 41 via thefirst image processing circuit 31. Because of this, the number of piecesof image data stored in the first storage region 42 of the first buffermemory 41 is 2.

The control unit 32 checks N, which is the number of pieces of imagedata stored in the first storage region 42 of the first buffer memory41. The control unit 32 makes a determination by comparison between thenumber of pieces of image data N within the first storage region 42 anda threshold value N₀ (in the present embodiment, N₀=1).

For example, in the above-described determination by comparison, whenthe control unit 32 determines that the number of pieces of image data Nwithin the first storage region 42 is equal to or less than thethreshold value N₀, it indicates that image data to be obtained newly isinput to the first image processing unit 31 after image processing forthe image data has been completed. That is, it is possible to performthe image processing on the image data obtained continuously in thecontinuous shooting mode only in the first image processing circuit 31.In this case, the first image processing circuit 31 does not output theoperation signal toward the second image processing circuit 36. As aresult of this, the second image processing circuit 36 enters thestandby state.

In contrast, when the control unit 32 determines that the number ofpieces of image data N exceeds the threshold value N₀, it indicates thatimage data to be obtained newly is input to the first image processingcircuit 31 before the image processing for the image data is completed.This case indicates that the rate of image processing in the first imageprocessing circuit 31 cannot keep pace with the rate at which the imagedata is written to the first buffer memory 41, that is, it is notpossible to keep pace only by the image processing in the first imageprocessing circuit 31. In this case, the control unit 32 outputs theoperation signal toward the second image processing circuit 36.

Upon receipt of the operation signal from the first image processingcircuit 31, the control unit 37 switches the standby state of the secondimage processing circuit 36 to the operation state. It should be notedthat “activation” in FIG. 2 represents processing to switch the standbystate to the operation state. During the period of this processing time,the control unit 37 supplies electric power to the image processing unit38, the coding/decoding unit 39. At the same time, the control unit 37supplies electric power to the second buffer memory 45. Furthermore, thecontrol unit 37 outputs a clock pulse to the image processing unit 38,the coding/decoding unit 39, and the second buffer memory 45. Because ofthis, the second image processing circuit 36 and the second buffermemory 45 are operated.

For example, when the activation time of the second image processingcircuit 36 is shorter than the output interval of image data, the secondimage processing circuit 36 causes the first storage region 46 of thesecond buffer memory 45 to store image data obtained by the thirdimaging. In contrast, the activation time of the second image processingcircuit 36 is stored in advance in the first image processing circuit31, and thus, when the image data obtained is input to the first imageprocessing circuit 31 after the second image processing circuit 36 isswitched to the operation state, the image data is processed as invaliddata.

After that, image data obtained by the fourth, sixth, eighth, and tenthshooting is stored in the first buffer memory 41 and image data obtainedby the fifth, seventh, and ninth shooting is stored in the second buffermemory 45. That is, image data obtained by the third and latter shootingis stored alternately. It should be noted that in FIG. 1, the image dataobtained by the first shooting is described as first image data, imagedata obtained by the second shooting is described as second image data,and so on. Furthermore, the coded data corresponding to the image datais represented as first coded data, second coded data, and the like.

When the image data is written to any of the first buffer memory 41 andthe second buffer memory 45 also, the image processing and codingprocessing by the first image processing circuit 31 and the second imageprocessing circuit 36 are performed. For example, in the first imageprocessing circuit 31, when image data obtained by the second shootingis recorded in the first buffer memory 41, the image processing for theimage data obtained by the first shooting is started. Then, when theimage processing is completed, the coding processing by thecoding/decoding unit 33 is performed and coded data is generated. Itshould be noted that the coded data is stored in the second storageregion 43 of the first buffer memory 41. Following this, image data fromwhich the coded data is generated is deleted.

Afterward, in the step in which image processing in the first imageprocessing circuit 31 is performed, new image data is written to thefirst storage region 42 of the first buffer memory 41. That is, thefirst storage region 42 of the first buffer memory 41 is required onlyto have a capacity large enough to store three pieces of image data, andthus, it is made possible to save the capacity of the first buffermemory 41. Similarly, in the second image processing circuit 36, in thestep in which image processing for the image data obtained by the thirdimaging is performed, image data obtained by the fifth shooting isstored in the first storage region 46 of the second buffer memory 45.That is, afterward, in the step in which image processing in the firstimage processing circuit 31 is performed, new image data is written tothe first storage region 42 of the first buffer memory 41. In the firststorage region 46 of the second buffer memory 45, up to two pieces ofimage data are stored, and thus, the first storage region is requiredonly to have a capacity large enough to store two pieces of image data.

When image processing for the image data stored in the first storageregion of the corresponding buffer memory is performed in the firstimage processing circuit 31 and the second image processing circuit 36,respectively, image processing and coding processing in, for example,the second image processing circuit 36 are completed earlier. When thecoding processing is completed in the second image processing circuit36, the second image processing circuit 36 reads coded data stored inthe second storage region 47 of the second buffer memory 45 and outputsit to the first image processing circuit 31. The first image processingcircuit 31 writes the input coded data to the second storage region 43of the first buffer memory 41. Then, when the image processing andcoding processing in the first image processing circuit 31, and write ofthe coded data from the second image processing circuit 36 to the secondstorage region 43 of the first buffer memory 41 are completed, thecontrol unit 32 of the first image processing circuit 31 outputs theoperation stop signal to the second image processing circuit 36.

Upon receipt of the operation stop signal from the first imageprocessing circuit 31, the control unit 37 of the second imageprocessing circuit 36 stops the supply of a clock pulse to the imageprocessing unit 38, the coding/decoding unit 39, and the second buffermemory 45 and stops the supply of electric power to the image processingunit 38, the coding/decoding unit 39, and the second buffer memory 45.

It should be noted that when the number of pieces of image data N withinthe first storage region 42 is equal to or less than the threshold N₀,that is, when continuous shooting at a low frame rate is performed orwhen shooting in the still image mode is performed, the second imageprocessing circuit 36 remains in the standby state and no electric poweris supplied to the image processing unit 38 and the coding/decoding unit39 of the second image processing circuit 36, and thus, it is madepossible to prevent electric power from being wasted. As describedabove, when the primary battery or secondary battery is used as a powersource device, it is made possible to lengthen the lifetime of thesebatteries. Furthermore, the second image processing circuit 36 isbrought into the standby state, and thus, it is possible to reduce theamount of heat generated from the circuit involved in image processingand to suppress the deformation of the interior of the digital camera orthe risk of burn. Moreover, because it is possible to keep to a minimumthe capacity of the first buffer memory 41 and the first storage region46 of the first storage region 42, and thus, it is also possible toreduce the total capacity of the buffer memory.

Second Embodiment

A second embodiment of the present invention will be explained belowusing the drawings. Meanwhile, the second embodiment is a modificationof the first embodiment in which the basis for determination of controlis different, and thus, only parts different from those in the firstembodiment are explained. Furthermore, the same configuration as that ofthe first embodiment is explained by using the same symbol.

Next, the flow of processing in the first image processing circuit 31and the second image processing circuit 36 when shooting is performed inthe continuous shooting mode in the second embodiment is explained usingthe timing chart in FIG. 3. Meanwhile, in the timing chart in FIG. 3, acase is explained, where 10 images are shot continuously in thecontinuous shooting mode at a frame rate value of 8 fps. Each frameimage in FIG. 3 corresponds to each piece of image data shown in FIG. 1.That is, the frame image 1 corresponds to the first image data shown inFIG. 1 and the frame image 2 corresponds to the second image data shownin FIG. 1, respectively. It should be noted that immediately before thetiming chart in FIG. 3 is performed, the second image processing circuit36 is in the standby state.

Then, as in the first embodiment, starting from the operation of therelease button 55, imaging is performed and image data input to thefirst image processing circuit 31 is written to the first storage region42 of the first buffer memory 41. For example, when the image signal isone obtained by the first imaging, the number of pieces of image datastored in the first storage region 42 of the first buffer memory 41is 1. Triggered by this, the control unit 32 of the first imageprocessing circuit 31 starts to measure time.

Then, when 0.125 seconds elapse after the first imaging, the secondimaging is performed. Image data based on the second imaging is writtento the first storage region 42 of the first buffer memory 41 via thefirst image processing circuit 31. Because of this, the number of piecesof image data stored in the first storage region 42 of the first buffermemory 41 is 2. At the same time, the control unit 32 stops measuring oftime.

The control unit 32 calculates an output interval T of the image data byfinding the time when measuring of time is stopped, in other words, atime elapsed from when the image signal obtained by the first imaging isinput to the first buffer memory 41 to when the image signal obtained bythe second imaging is input to the first buffer memory 41. The controlunit 32 makes a determination by comparison between the output intervalT of the image data and a threshold value T₀. It should be noted thatthe threshold value T₀ is a processing time required for the imageprocessing of image data in the first image processing circuit 31.

For example, in the above-described determination by comparison, if thecontrol unit 32 determines that the output interval T of the image dataexceeds the threshold value T₀, this indicates that the image data to beobtained newly is input to the first image processing unit 31 after theimage processing for the image data has been completed. That is, it ispossible to perform the image processing on the image data obtainedcontinuously in the continuous shooting mode only in the first imageprocessing circuit 31. In this case, the first image processing circuit31 does not output the operation signal toward the second imageprocessing circuit 36. As a result of this, the second image processingcircuit 36 enters the standby state.

In contrast, when the control unit 32 determines that the outputinterval T is equal to or less than the threshold value T₀, thisindicates that the image data to be obtained newly is input to the firstimage processing unit 31 before the image processing for the image datais completed. This case indicates that the rate of the image processingin the first image processing circuit 31 cannot keep pace with the rateat which image data is written to the first buffer memory 41, that is,it is not possible to keep pace only by the image processing in thefirst image processing circuit 31. In this case, the control unit 32outputs the operation signal toward the second image processing circuit36.

Upon receipt of the operation signal from the first image processingcircuit 31, the control unit 37 switches the standby state of the secondimage processing circuit 36 to the operation state. It should be notedthat “activation” in FIG. 3 represents the processing to switch thestandby state to the operation state. During the period of thisprocessing time, the control unit 37 supplies electric power to theimage processing unit 38, the coding/decoding unit 39. At the same time,the control unit 37 supplies electric power to the second buffer memory45. Furthermore, the control unit 37 outputs a clock pulse to the imageprocessing unit 38, the coding/decoding unit 39, and the second buffermemory 45. Because of this, the second image processing circuit 36 andthe second buffer memory 45 are operated. Afterward, the same processingas that in the first embodiment is performed.

It should be noted that when the output interval T of the image dataexceeds the threshold value T0, that is, when continuous shooting at alow frame rate value is performed or when shooting is performed in thestill image mode, the second image processing circuit 36 remains in thestandby state and no electric power is supplied to the image processingunit 38, the coding/decoding unit 39 of the second image processingcircuit 36, and thus, it is made possible to prevent electric power frombeing wasted. As described above, when the primary battery or thesecondary battery is used as a power source device, it is made possibleto lengthen the lifetime of these batteries. Furthermore, the secondimage processing circuit 36 is brought into the standby state, and thus,it is possible to reduce the amount of heat generated from the circuitinvolved in image processing and to suppress the deformation of theinterior of the digital camera and the risk of burn. Moreover, it ispossible to keep to a minimum the capacity of the first buffer memory 41and the first storage region 46 of the first storage region 42, andthus, it is also possible to reduce the total capacity of the buffermemory.

In the present embodiment, the output interval of image data is measuredand whether or not the measured output interval of image data exceedsthe threshold value is determined, but this is not limited and forexample, it may also be possible to measure an output interval of ahorizontal synchronizing signal in the imaging element. Furthermore, inaddition to the above, it may also be possible to compare the frame ratevalue with the threshold value using the frame rate value in thecontinuous shooting mode. In this case, it is also possible to operatethe second image processing circuit only in a high continuous shootingmode by providing a plurality of continuous shooting modes the framerate values of which are different, where the continuous shooting modeat a low frame rate value is referred to as a low continuous shootingmode and the continuous shooting mode at a high frame rate value isreferred to a high continuous shooting mode. It should be noted that itis possible to set the frame rate value by the operation of the settingoperation unit 55.

In the present embodiment, it is assumed that the processing capacityrelating to image processing is the same in the first image processingcircuit and the second image processing circuit, but this is notlimited. For example, when there are two image processing circuitshaving different image processing capacities, the image processingcircuit having the higher processing capacity relating to imageprocessing is caused to operate at all times and the other imageprocessing circuit is caused to operate based on the output interval ofimage data.

In the present embodiment, the example is taken, where there are twoimage processing circuits, that is, the first image processing circuit31 and the second image processing circuit 36, but this is not limitedand it may also be possible to provide three or more image processingdevices and to determine the number of image processing circuits causedto operate based on the output interval of image data.

In the present embodiment, whether or not to operate the second imageprocessing circuit 36 is determined based on the output interval ofimage data obtained, but it may also be possible to determine whether ornot to operate the second image processing circuit 36 based on theoutput resolution of image data output from the imaging element 16 orthe data capacity of the image data in addition to the output intervalof the image data. For the output resolution, when the output resolutionof the image data is a high resolution that exceeds a predeterminedthreshold value, the second image processing circuit 36 is caused tooperate. For the data capacity of image data, the data capacity isestimated based on the output resolution of the image data and when thedata capacity exceeds a predetermined threshold value, the second imageprocessing circuit 36 is caused to operate.

The many features and advantages of the embodiments are apparent fromthe detailed specification and, thus, it is intended by the appendedclaimed to cover all such features and advantages of the embodimentsthat fall within the true spirit and scope thereof. Further, sincenumerous modifications and changes will readily occur to those skilledin the art, it is not desired to limit the inventive embodiments to theexact construction and operation illustrated and described, andaccordingly all suitable modifications and equivalents may be resortedto, falling within the scope thereof.

1. An electronic camera comprising: an imaging element whichcontinuously outputs image data obtained by photoelectrically convertingobject light; a buffer memory which temporarily stores image data beingoutput from the imaging element; a plurality of image processing unitswhich are capable of performing image processing on image data outputfrom the imaging element; and a control unit which causes an imageprocessing unit of the plurality of image processing units to operatebased on a number of pieces of the image data stored in the buffermemory when the image data is output continuously from the imagingelement, in which the image processing unit performs image processing oneach piece of image data output continuously.
 2. The electronic cameraaccording to claim 1, wherein the plurality of image processing unitsinclude a first image processing unit which operates regardless of anoutput state of image data output from the imaging element and a secondimage processing unit operated by the control unit, and the control unitcauses the second image processing unit to operate based on the numberof pieces of the image data stored in the buffer memory.
 3. Theelectronic camera according to claim 1, wherein the control unit causesthe image processing unit that performs image processing on each pieceof the image data output continuously to operate based on a result of acomparison between the number of pieces of the image data stored in thebuffer memory and a threshold value set in advance.
 4. The electroniccamera according to claim 3, wherein the control unit causes the imageprocessing unit that performs image processing on each piece of theimage data output continuously to operate when the number of pieces ofthe image data stored in the buffer memory exceeds the threshold value.5. An electronic camera comprising: an imaging element whichcontinuously outputs image data obtained by photoelectrically convertingobject light; a plurality of image processing units which are capable ofperforming image processing on image data output from the imagingelement; and a control unit which causes an image processing unit of theplurality of image processing units to operate based on an outputinterval of the image data when the image data is output continuouslyfrom the imaging element, in which the image processing unit performsimage processing on each piece of image data output continuously.
 6. Theelectronic camera according to claim 5, wherein the plurality of imageprocessing units include a first image processing unit which operatesregardless of an output state of image data output from the imagingelement and a second image processing unit operated by the control unit,and the control unit causes the second image processing unit to operatebased on the output interval of the image data.
 7. The electronic cameraaccording to claim 5, wherein the control unit causes the imageprocessing unit that performs image processing on each piece of imagedata output continuously to operate based on a result of a comparisonbetween the output interval of the image data and a threshold value setin advance.
 8. The electronic camera according to claim 7, wherein thecontrol unit causes the image processing unit that performs imageprocessing on each piece of the image data output continuously tooperate when the output interval of the image data is less than or equalto the threshold value.
 9. The electronic camera according to claim 5,wherein the output interval of the image data is obtained by measuring atime from a vertical synchronizing signal output at the time of start ofimaging to a vertical synchronizing signal to be output next.
 10. Theelectronic camera according to claim 5, comprising a setting operationunit to be operated when setting the output interval of the image data.11. An electronic camera comprising: an imaging element whichcontinuously outputs image data obtained by photoelectrically convertingobject light; a plurality of image processing units which are capable ofperforming image processing on mage data output from the imagingelement; and a control unit which causes an image processing unit of theplurality of image processing units to operate based on an outputresolution of the image data output from the imaging element when theimage data is output continuously from the imaging element, in which theimage processing unit performs image processing on each piece of imagedata output continuously.
 12. The electronic camera according to claim11, wherein the plurality of image processing units include a firstimage processing unit which operates regardless of an output state ofimage data output from the imaging element and a second image processingunit operated by the control unit, and the control unit causes thesecond image processing unit to operate based on the output resolutionof the image data.
 13. The electronic camera according to claim 11,wherein the control unit causes the image processing unit that performsimage processing on each piece of the image data output continuously tooperate based on a result of a comparison between the output resolutionof the image data and a threshold value set in advance.
 14. Theelectronic camera according to claim 13, wherein the control unit causesthe image processing unit that performs image processing on each pieceof the image data output continuously to operate when the outputresolution of the image data exceeds the threshold value.
 15. Theelectronic camera according to claim 1, wherein the control unit stopsthe image processing unit operated by the control unit when imageprocessing is completed in at least each of the image processing unitsoperated.
 16. The electronic camera according to claim 5, wherein thecontrol unit stops the image processing unit operated by the controlunit when image processing is completed in at least each of the imageprocessing units operated.
 17. The electronic camera according to claim11, wherein the control unit stops the image processing unit operated bythe control unit when image processing is completed in at least each ofthe image processing units operated.